Legend of the Birth of the Ganga
Once upon a time there was a group of demons who used to tease Brahmin hermits and upset their prayers. When chased away, they would hide in the ocean, but return at night to resume their teasing. The ascetics then asked the sage Agastya to free them from the torture of temptation. Wishing to help, Agastya chose the easiest course, and swallowed the whole ocean, including the devils. The temptations thus came to an end but the earth was left without water. Men then had to appeal to another sage, Bhagiratha, to deliver them from the scourge of drought. In order to be worthy of a godly boon of such magnitude, Bhagiratha spent a thousand years in ascetic practices and then went before Brahma and asked him to let the heavenly river Ganga—one of the milky ways in the firmament—fall upon the earth.
Brahma, satisfied with the tapasya (ascetic performances) of Bhagiratha, promised to try his best, adding that he would first have to persuade Shiva to help him. He explained that if the great heavenly river fell upon the earth with all the force and immeasurable weight of its waters, earthquakes and unheard of destruction would result. Consequently, someone should interpose himself to absorb the shock of the falling water, and nobody else could do so save the almighty Shiva.
Bhagiratha continued his fastings and his prayers, and the time came when Shiva was moved. He allowed the Ganga to let her waters flow upon the earth and interposed his own head between the sky and the earth to lessen its impact. The heavenly waters then flowed smoothly through his divine hair into the Himalayas, and from there into the Indian plains, bringing prosperity, blessings from heaven, and the remission of sins.